The present invention relates to an optical coupling device, a manufacturing method thereof, and a power conversion system.
A photocoupler has a light emitting element, such as a light emitting diode, and a light receiving element, such as a phototransistor, and transmits an electrical signal by converting an inputted electrical signal into light with the light emitting element and by returning the light to the electrical signal with the light receiving element.
A photocoupler is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2008-189833 (Patent Document 1), in which a light emitting element and a light receiving element are sealed by a cured product of a thermosetting epoxy resin composition.
Also, a photocoupler using a primary sealing resin and a secondary sealing resin is disclosed in Japanese Unexamined Patent Application Publication No. 2014-33124 (Patent Document 2). The primary sealing resin contains an epoxy resin for primary sealing, a phenolic resin curing agent for primary sealing, an inorganic filler for primary sealing, and fatty acid wax for primary sealing; and the secondary sealing resin contains an epoxy resin for secondary sealing, a phenolic resin curing agent for secondary sealing, an inorganic filler for secondary sealing, and fatty acid wax for secondary sealing. At least one of the resin for primary sealing and the resin for secondary sealing contains fatty acid amide wax.
Also, an optical semiconductor device sealed by a cured product of an epoxy resin composition is disclosed in Japanese Unexamined Patent Application Publication No. 2005-239901 (Patent Document 3). The epoxy resin composition is one whose main components are an epoxy resin (A) having two or more epoxy groups in one molecule, a phenolic resin curing agent (B), a curing accelerator (C), and fused crushed silica (D). The epoxy resin composition further contains a phenolic antioxidant (E) as an essential component. Additionally, the light transmittance of a cured product of the epoxy resin composition, the product having a thickness of 1 mm, is 15% or more for the light having a wavelength of from 700 nm to 1000 nm, and the light transmittance retention rate thereof after being subjected to 125 ° C. for 1000 hrs is 50% or more for the light having a wavelength of 720 nm.